A strategy for selective N-acylation of purine and pyrimidine bases of deoxy and ribo nucleosides.

Abstract

A novel cost effective N-acylation procedure for exocyclic amino function of ribonucleosides (adenosine/guanosine/cytidine) and deoxynucleosides (adenosine/guanosine/cytidine) has been developed. In the present method the acids used for acylation were activated by preparing their corresponding p-nitrophenyl esters. These esters couple with - NH(2) group in presence of dicyclohexylcarbodiimide as coupling agent and catalysts viz. DMAP, HOBT & HOSu to give the--CO-NH- bond; a well-established strategy in peptide synthesis. To minimise the contamination of DCU, different combinations of activated ester and nucleosides has been used. The use of catalysts viz. DMAP, HOBt & HOSu enhanced the yields. HOSu was found to give best results.